The present invention relates generally to various apparatus and methods for protecting liquids within a container, such as a reaction vessel or a storage vessel, from the adverse effects of high temperature. Where the liquids contained in such vessels are exposed to undesirably high temperatures, the vessel may be damaged or explode, or its emergency venting system may be activated.
While safety venting systems such as safety valves, rupture disks, and other components may appear to provide some protection against adverse consequences. This is not the case where the liquid sought to be protected is toxic, for example. In such cases, simply venting its container and allowing spillage is sometimes just as undesirable as allowing the vessel to leak or burst. Even if the liquid sought to be protected is not toxic, it is still clearly desirable to protect against explosion or venting in the first instance rather than permitting venting as an emergency arises and then trying to reduce the impact of such emergency venting.
It is known that liquid vessels may be protected by active or passive safety systems; by "active" system is meant one which requires extrinsic support of some kind for its operation. By a "passive system" is meant one which does not require the functioning of auxiliary equipment, such as pumps, motors, or extrinsically operated relief valves, etc. Passive systems include those having rupture disks or means for transferring heat from the body of the liquid, for example, to a heat exchange area without the operation of pumps, motors, valves, or the like.
In this connection, certain embodiments of the present invention are an improvement to the passive systems disclosed in U.S. Pat. No. 4,741,881.
Referring again to the general nature of the present invention, various chemicals, particularly including liquid chemicals undergoing a reaction, or those in storage, may be extremely safe when held within certain temperature limits, and yet hold out a serious risk of injury or even death to personnel. Such materials also create risks of damage to equipment, and/or to the surrounding environment, this risk may arise if the liquid temperature is permitted to attain a certain level. These circumstances can be aggravated if the temperature of the vessel contents is increasing at a rapid rate. Consequently, there is a need for apparatus and methods to ensure that, even under unexpected circumstances, unintended temperature rise in contained liquids is prevented or minimized.
According to the invention, a protective fluid is used as a combination heat sink and portion of a heat transfer mechanism, and different forms of apparatus are provided so that, whether the protected fluid is self-heated or is heated from outside sources, protection will be automatically provided.
Thus, in the case of an protected liquid wherein the principal hazard is exposure to exterior high temperatures coming from outside the storage vessel, a protective liquid is arranged as a shroud or the equivalent in the sense of covering at least one surface, and preferably most or all exposed surfaces of the container. A liquid of this sort may in some cases act as a sacrificial liquid in the sense that heat transferred to it may be boiled away at a temperature below the danger point for the protected fluid.
In other instances, the principal source of high temperature is the interior of the protected fluid itself. In these instances, the apparatus is constructed and arranged so that upon temperature rise within the body of the protected liquid, an exterior liquid is caused to circulate and/or vaporize, and in so doing, is caused to withdraw heat from the interior of the protected liquid without permitting the temperature of the protected liquid to rise unduly. In all cases, the temperature of the coolant liquid is selected so as to circulate and, in most cases, boil, well below a given temperature at which the protected liquid would become dangerous. The circulation and/or boiling temperature of the coolant liquid may be referred to as a threshold temperature, i.e., temperature at which significant protective action begins. The danger temperature is a temperature at which the protected liquid becomes dangerous. Significant heat exchange and/or evaporation occurs between these temperatures.
Various apparatus are described in detail, including those having tanks which include bayonet tubes, cooling coils, and/or top and/or sidewall jacketing providing large surface area contact between the protected liquid and the liquid coolant.
In view of the failure of the prior art to furnish effective protective mechanisms for certain fluids which are dangerous at certain predetermined "danger" temperatures, particularly those wherein, for reasons of toxicity, for example, ordinary venting is dangerous or undesirable for use as a safety measure, it is an object of the invention to provide a storage or reaction vessel adapted to protect liquids which prevent serious safety hazards to personnel, equipment, and/or the environment against fire, explosion, or accidental discharge to the atmosphere.
It is also an object of the invention to provide one or more apparatus which are able to provide for absorption by a liquid coolant of heat which might undesirably raise the temperature of a protected liquid.
Another object of the invention is to provide an apparatus which positions a liquid coolant in heat exchange relation with a protected liquid in such a way that the coolant provides a significant heat storage and dissipation capacity in relation to the heat capacity of the protected liquid.
A further object of the invention is to provide a method of protecting liquids against undue temperature rise by exchanging heat which might cause a temperature rise in the protected liquid between the protected liquid and/or an exterior source and a liquid coolant which achieves cooling action by circulation and/or vaporization.
Another object of the invention is to provide various forms of retention apparatus for protective liquids, which apparatus is relatively easy to construct and can be fabricated at reasonable cost by known techniques.
Yet another object of the invention is to provide a series of containers for liquids, which containers have known advantages and characteristics in use, including the ability to reflux a coolant liquid kept in intimate heat exchange with the body of the protected liquid as a method of withdrawing heat from the mass of protected liquid.
Another object of the invention is to provide an apparatus which takes advantage of the ability of a liquid coolant to absorb heat by convection or vaporization by maintaining the coolant in intimate heat exchange relation with the heat source.
Still another object of the invention is to provide a protective apparatus which includes an inner storage chamber for a protected liquid, an outer chamber with some of its surfaces exposed to the atmosphere and its other surfaces in contact with the exposed surfaces of the protected liquid chamber, with at least the sidewall surfaces of the inner chamber being covered by a liquid coolant disposed in the outer chamber, means for venting vapor from the headspace in the outer chamber vessel, and means for establishing an intimate heat exchange relation between the anticipated source of heat and the liquid coolant.
A still further object of the invention is to provide a composite vessel arrangement for a protected liquid wherein a first, fluid tight chamber for a protected liquid is provided, wherein the first chamber has a major portion of its exterior surrounded by a liquid coolant having a vaporization temperature below a temperature at which the protected liquid presents a fire or explosion hazard, and conduit means providing for movement of the liquid coolant through the body of the protected liquid by convection to establish heat exchange between the coolant and the contents of the protected liquid tank, particularly wherein such means include helical coils or the like and/or bayonet tubes each having one end portion disposed within the body of liquid coolant and the other in the body of the protected liquid.
Another object of the invention is to provide a liquid protective system wherein a coolant chamber at least partially surrounds a chamber for a protected liquid, wherein the protected liquid chamber includes a rupture disk and an outlet terminating in a diffuser unit disposed below the upper surface of the liquid in the coolant chamber, with the coolant fluid being maintained in heat exchange relation with the protected liquid, and wherein vent means are provided to permit whatever coolant is vaporized by heat exchange to pass to the atmosphere outside the coolant tank, whereby additional protection is provided against discharge of the protected liquid to the atmosphere.
A still further object of the invention is to provide a composite vessel which includes a chamber for a protected liquid and a liquid coolant chamber having portions surrounding and in heat exchange relation with the walls of the protected liquid chamber, and wherein plural tubes are arranged with portions thereof lying in each chamber to provide a refluxing type of heat exchange action between the body of the protected liquid and the body of the coolant.
Yet another object of the invention is to provide an arrangement providing a first liquid coolant for a protected liquid, and a third liquid acting as a medium for heat exchange between the two other liquids.
The foregoing and other objects and advantages of the invention are achieved in practice by providing methods and apparatus taking advantage of a heat exchange relation between a liquid coolant and a protected liquid, whereby vaporization of the liquid coolant withdraws heat from the body of the protected liquid or an exterior heat source in order to prevent undue temperature rise within the body of the protected liquid. The invention also achieves its objects and advantages by providing liquid containers which include means for providing heat exchange contact and/or circulation between bodies of coolant liquids and protected liquids, respectively.
The exact manner in which the foregoing and other objects and advantages are achieved in practice will become more clearly apparent when reference is made to the following detailed description of the preferred embodiments of the invention set forth by way of example, and shown in the accompanying drawings, wherein like reference numbers indicate corresponding parts throughout.